The Waterborne Symposium 2025

Co-Authors:  Kaden Stevens, Jeff Aguinaga, Derek Patton, Brent Sumerlin, and Tristan Clemons

Abstract

Carbon fiber has been established as one of the most important structural materials of the 21st century because of its remarkably high strength to weight ratio. As such, carbon fiber has found a wide range of applications in sporting goods, aerospace, construction, and medical device industries. Currently, approximately 90% of carbon fibers are derived from polyacrylonitrile (PAN) precursors due to the superior tensile strength that can be achieved when processed effectively. Traditional PAN synthesis is achieved by employing free radical polymerization in solution or by emulsion, resulting in broad molecular weight distributions. Additionally, PAN is insoluble in its own monomer and requires toxic organic solvents such as dimethylformamide (DMF), dimethyl sulfoxide, or ethylene carbonate for both solution polymerization and wet spinning into white fibers. Controlled radical polymerization techniques have demonstrated that narrow molecular weight distributions can provide favorable rheological profiles for fiber spinning but suffer from low monomer conversions and struggle to achieve molecular weights necessary for producing high quality carbon fibers. In this study, we present an aqueous photoiniferter (aqPI) polymerization of acrylonitrile, achieving high molecular weights of PAN at high monomer conversions, with significantly faster kinetics, and greater control of polymer dispersity when compared to traditional approaches reported. Polymerization kinetics were determined by 1H nuclear magnetic resonance (NMR) spectroscopy, and polymer molecular weight and dispersity (PDI) determined by gel permeation chromatography (GPC). Residual zinc content was quantified by X-ray photoelectron spectroscopy (XPS).